Apparatuses for steam separation, and nuclear boiling water reactors including the same

ABSTRACT

According to at least some example embodiments, a dome collector separation stage includes an inner side wall that defines an inner channel; and an outer side wall that, together with the inner side wall, defines an outer channel, the inner channel being configured to receive a two-phase flow stream (FS) of water and steam, and pass the two-phase FS to the outer channel via inlets included in the inner side wall, the outer channel being configured to separate at least some water from the two-phase FS, and pass moisture-reduced steam out of the steam separator stage via outlets included in the outer side wall.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.16/736,044, filed Jan. 7, 2020, which is a divisional of U.S.application Ser. No. 15/492,163, filed on Apr. 20, 2017, the entirecontents of each of which are hereby incorporated by reference.

BACKGROUND Field

Example embodiments relate to steam separation systems for a nuclearboiling water reactor.

Description of Related Art

A boiling water nuclear reactor generates steam by utilizing heatgenerated from a core and rotates a turbine and a power generator bymeans of the steam. In a pressurized water nuclear reactor, coolingwater separately flows into a primary cooling system circulating throughthe nuclear reactor, and a secondary cooling system serving as a steamgenerator. In the primary cooling system, high-temperature water isgenerated by the heat generated from the nuclear reactor core. In thesecondary cooling system, water in the secondary cooling system isboiled in a heat exchanger in the steam generator to become steam, whichrotates a turbine or a power generator.

Regardless of the reactor type, moisture must be removed from the steamto be supplied to the turbine. To this end, a typical reactor isprovided with a plurality of steam separators, dryers and the like so asto remove water from a two-phase flow of steam and water generated inthe nuclear reactor or the steam generator.

In a conventional steam separator, even if the water separated from thetwo-phase flow that has flowed in the steam separator is dischargedoutside the barrel through the water discharge pipe, most of the steamflows out from the upper part of the barrel. Therefore, if the two-phaseflow stream (FS) velocity is high and/or steam separator inlet moisturecontent is high, the number of the minute droplets that are carried bythe steam is increased, which may result in an increase in moisturecarry-over. The increase in moisture carry-over increases theradioactivity levels in the plant and adversely affects outageperformance. For example, liquid water droplets may transportradioactive particles from the reactor to the balance of plant (BoP).These particles may deposit in various components in the main steam lineand turbine and increase the radiation exposure to reactor personnel. Ifthe moisture carry-over levels become undesirably high, certaincomponents of the main steam line and turbine can be adversely impactedas a result of enhanced degradation from such mechanisms such as flowaccelerated corrosion leading to higher maintenance costs.

SUMMARY

According to at least some example embodiments, a dome collectorseparation stage includes an inner side wall that defines an innerchannel; and an outer side wall that, together with the inner side wall,defines an outer channel, the inner channel being configured to receivea two-phase flow stream (FS) of water and steam, and pass the two-phaseFS to the outer channel via inlets included in the inner side wall, theouter channel being configured to separate at least some water from thetwo-phase FS, and pass moisture-reduced steam out of the steam separatorstage via outlets included in the outer side wall.

The steam separator stage may include an upper section and a lowersection, the inlets in the inner side wall and the outlets in the outerside wall may be included in the upper section, and a portion of theouter side wall within the upper section may be curvilinear such thatthe outer channel is configured to cause the at least some water toseparate from the two-phase FS when the two-phase FS impacts thecurvilinear portion of the outer side wall, due to a density differencebetween water and steam portions of the two-phase FS.

The outer channel may be configured such that the at least some waterseparated from the two-phase FS by the outer channel exits the domecollector separation stage through a portion of the outer channel withinthe lower section of the dome collector separation stage.

A nuclear boiling water reactor may include a reactor pressure vessel; acore in the reactor pressure vessel; a plurality of steam separatorslocated above the reactor core; and the dome collector separation stagelocated above the plurality of steam separators.

The plurality of steam separators may include a plurality of peripheralsteam separators located in a peripheral portion of an interior space ofthe reactor pressure vessel, and the dome collector separation stage maybe vertically aligned with the plurality of peripheral steam separatorssuch that the inner channel is configured to receive the two-phase FSfrom the peripheral steam separators.

According to at least some example embodiments, a steam separationsystem includes a steam separator; and an elbow extension attached tothe steam separator, the elbow extension including a channel, the elbowextension being configured to receive a two-phase flow stream (FS) ofwater and steam from the steam separator, separate at least some waterfrom a two-phase FS, and pass the separated at least some water throughthe channel and out of an exit portion of the elbow extension.

The elbow extension may include a curved section configured to cause theat least some water to separate from the two-phase FS due to acentripetal force exerted on the two-phase FS as a result of thetwo-phase FS flowing through the curved section.

A convex surface of a portion of the channel within the curved sectionmay include a plurality of extraction holes configured to passmoisture-reduced steam from the channel out of the elbow extension.

A nuclear boiling water reactor may include a reactor pressure vessel; acore in the reactor pressure vessel; and one or more of the steamseparation systems.

The one or more steam separation systems may be located in a peripheralportion of an interior space of the reactor pressure vessel such thatthe exit portion of each of the one or more steam separation systemsfaces an inner surface of a side wall of the reactor pressure vessel.

According to at least some example embodiments, a steam separatorincludes a skirt; a barrel inside the skirt; a first separator stage;and a second separator stage adjacent to the first separator stage, thefirst separator stage including a first pick-off ring that protrudesfrom the skirt past the barrel towards an interior of the steamseparator, the second separator stage including an inner surface whichhas a diameter that gradually increases from a first diameter value at afirst portion of the second separator stage to a second diameter valueat a second portion of the second separator stage.

The first portion of the second separator stage may be a portion of thesecond separator stage adjacent to the first pick-off ring of the firstseparator stage, and the second portion of the second separator stagemay be a portion of the second separator located farther away from thefirst pick-off ring of the first separator stage than the first portion.

The first diameter value may be equal to a diameter value of an innersurface of the first pick-off ring.

The steam separator may further include a standpipe connected to thefirst separator stage, wherein the first separator stage furtherincludes turning vanes, the standpipe being connected to an end of thefirst separator stage opposite an end of the first separator stage atwhich the first pick-off ring is located.

A nuclear boiling water reactor may include a reactor pressure vessel; acore in the reactor pressure vessel; and one or more of the steamseparators located above the reactor core.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of non-limiting example embodimentsherein may become more apparent upon review of the detailed descriptionin conjunction with the accompanying drawings. The accompanying drawingsare merely provided for illustrative purposes and should not beinterpreted to limit the scope of the claims. The accompanying drawingsare not to be considered as drawn to scale unless explicitly noted. Forpurposes of clarity, various dimensions of the drawings may have beenexaggerated.

FIG. 1 is a cross-sectional view of at least a portion of a nuclearboiling water reactor (BWR) according to an example embodiment.

FIG. 2 illustrates peripheral steam separators among the steamseparators of the BWR.

FIGS. 3A-3C illustrate various views of portions of a dome collectoradditional separation stage according to at least some exampleembodiments.

FIGS. 4A-4C are diagrams illustrating an example position of the domecollector within the BWR according to at least some example embodiments.

FIG. 5 is a diagram illustrating an example operation of the domecollector.

FIGS. 6A-6E illustrate various views of portions of an elbow extensionadditional separation stage according to at least some exampleembodiments.

FIG. 7 is a diagram illustrating an example position of the elbowextension additional separation stage within the BWR according to atleast some example embodiments.

FIG. 8 illustrates a streamlined steam separator that includes pickoffrings.

FIG. 9 is a diagram for explaining the controlled expansion regions 4700between adjacent separator stages of the streamlined steam separator ingreater detail.

FIG. 10 is a diagram for explaining adjacent separator stages that lacka controlled expansion region.

DETAILED DESCRIPTION

It should be understood that when an element is referred to as being“on,” “connected to,” “coupled to,” or “covering” another element, itmay be directly on, connected to, coupled to, or covering the otherelement or intervening elements that may be present. In contrast, whenan element is referred to as being “directly on,” “directly connectedto,” or “directly coupled to” another element, there are no interveningelements present. Like numbers refer to like elements throughout thespecification. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items.

It should be understood that, although the terms first, second, third,etc. may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers, and/or sections should not be limited by these terms. Theseterms are only used to distinguish one element, component, region,layer, or section from another region, layer, or section. Thus, a firstelement, component, region, layer, or section discussed below could betermed a second element, component, region, layer, or section withoutdeparting from the teachings of example embodiments.

Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,”“upper,” and the like) may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It should be understood thatthe spatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” may encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

The terminology used herein is for the purpose of describing variousembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an,” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“includes,” “including,” “comprises,” and/or “comprising,” when used inthis specification, specify the presence of stated features, integers,steps, operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Example embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of exampleembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, example embodiments should not be construed aslimited to the shapes of regions illustrated herein but are to includedeviations in shapes that result, for example, from manufacturing.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments belong. Itwill be further understood that terms, including those defined incommonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand will not be interpreted in an idealized or overly formal senseunless expressly so defined herein.

BWR Structure Overview

FIG. 1 is a cross-sectional view of at least a portion of a nuclearboiling water reactor (BWR) according to an example embodiment.Referring to FIG. 1 , in the nuclear BWR 100, a plurality of steamseparators 1000 and a steam dryer system 500 having the structuredescribed below are disposed in a dome 16 at the upper portion of thereactor pressure vessel 6. The following is a description of thestructure inside the pressure vessel 6.

A cylindrical core shroud 8, which is concentric with the pressurevessel 6, is installed at a lower portion in the pressure vessel 6. Acore lower plenum 10 is formed in the lower portion of the shroud 8 inthe pressure vessel 6. A core 7 is disposed above this lower plenum 10and surrounded by the shroud 8. There is also a core upper plenum 11 cabove the core 7. A shroud head 12 a provided to the shroud 8 isdisposed above the upper plenum 11 c. It is to be noted that an annularspace 9 is formed between the pressure vessel 6 and the shroud 8, andfunctions as a circulation path for the light water coolant.

A prescribed number of holes (not shown) through which coolant passesare provided in the shroud head 12 a. The plurality of steam separators1000 are inserted into these holes and are aligned in parallel. The flowpaths that join the core 7 and the steam separator 1000 are connectedvia the upper plenum 11 c.

Also, a steam dryer system 500 is provided above the plurality of steamseparators 1000. A support structure 300 (e.g., a support ring as shown)supports the steam dryer system 500 above the steam separators 1000creating a dryer plenum 400 there between. A cylindrical dryer skirt350, connected to the support ring, extends downward from the supportstructure 300. A feed water inlet nozzle 17 and a steam outlet nozzle 15are provided at the side wall of the pressure vessel 6. Recirculationpumps 90 are provided at the lower portion of the reactor pressurevessel 6.

In the nuclear BWR 100, the wet steam generated in the core 7 by heatinglight water flows in each of the steam separators 1000 mounted on theshroud head 12 a via the upper plenum 11 c as a two-phase flow includingthe light water. In the steam separators 1000, the introduced gas-liquidtwo-phase flow stream (FS) passes through from the downward direction tothe upward direction. Thus, the gas of the gas-liquid two-phase FS maybe steam, and the liquid of the gas-liquid two-phase FS may be water.Steam containing moisture that could not be removed is supplied to thesteam dryer system 500 positioned above the steam separators 1000.

The steam (saturated steam) from which moisture is further removed bythe steam dryer system 500 is exhausted from the steam outlet nozzle 15and supplied to a turbine 2, for example, via a main steam line (notillustrated) between outlet nozzle 15 and the turbine 2. This steamdrives the turbine 2, which rotates a generator (not shown) joined tothe turbine 2, and thereby electrical power is generated. The steamexhausted from the turbine 2 is condensed at the condenser 3 and becomescondensed water. The condensed water, that is, the cooling water (lightwater) is supplied to a feed water heater 5 by a feed water pump 4. Thecooling water heated by the feed water heater 5 is re-introduced to thepressure vessel 6 from the feed water inlet nozzle 17.

Meanwhile, the water separated by the steam separators 1000 is mixedwith the cooling water supplied from the feed water inlet nozzle 17 anddescends the annular space 9 and is introduced to the core 7 via thelower plenum 10. At this time, the cooling water supplied to the core 7is pressurized by a pump 90, which can be either internal or external tothe nuclear BWR 100. As is discussed in greater detail below withrespect to FIG. 2 , at least some of steam separators 1000 areperipheral separators.

FIG. 2 illustrates peripheral steam separators among the steamseparators 1000. Referring to FIG. 2 , FIG. 2 is illustrated withrespect to a view position above the steam separators 1000 of FIG. 1(e.g., in-between support structure 300 and steam separators 1000) and aview direction that is parallel to longitudinal sides of the steamseparators 1000. As is illustrated in FIG. 2 , any or all of the steamseparators 1000 may be cylindrical in shape and have circular crosssections. Further, at least some of steam separators 1000 may beperipheral steam separators 1002. In the example shown in FIG. 2 , theperipheral steam separators 1002 are the separators located between, orsubstantially between, the two bold concentric circles illustrated inFIG. 2 . As is illustrated in FIG. 2 , peripheral steam separators 1002are steam separators located at or near a peripheral portion of anarrangement of the steam separators 1000. According to at least someexample embodiments, peripheral steam separators 1002 are steamseparators, from among steam separators 1000, that are located at ornear a peripheral portion of an interior of pressure vessel 6. As isillustrated in FIG. 2 , according to at least some example embodiments,the peripheral steam separators 1002 may be arranged in a ring shape.

According to at least some example embodiments, the gas-liquid two-phaseFS that passes through peripheral steam separators 1002 may include morewater than the gas-liquid two-phase FS passed by other steam separators(e.g., interior steam separators) among the steam separators 1000. Forexample, the gas-liquid two-phase FS that passes through peripheralsteam separators 1002 may include more water than steam.

Accordingly, it may be desirable to include, in the BWR 100, structuresfor removing or reducing the water passed by the peripheral steamseparators 1002, thereby preventing and/or reducing the exposure ofcomponents of the BWR 100 (e.g., a main steam line and/or a turbine 2)to prolonged high radioactivity levels during operation of the BWR 100.As a first example of such structure, a dome collector additionalseparation state according to at least some example embodiments will bediscussed below with reference to FIGS. 3A-5 . As a second example ofsuch structure, an elbow extension additional separation stage accordingto at least some example embodiments will be discussed below withreference to FIGS. 6A-7 . As a third example of such structure, astreamlined steam separator including separator pick-off rings accordingto at least some example embodiments will be discussed below withreference to FIGS. 8-10 .

Dome Collector Additional Separation Stage

FIGS. 3A-3C illustrate various views of portions of a dome collectoradditional separation stage 2000 according to at least some exampleembodiments. As will be discussed in greater detail below, according toat least some example embodiments, the dome collector additionalseparation stage 2000 may be provided in addition to the separators 1000to reduce the amount of water that is passed, within the gas-liquidtwo-phase FS, to at least some components of the BWR 100 (e.g., thedryer system 500, main steam line, and/or turbine 2). The dome collectoradditional separation stage 2000 may also be referred to, in the presentdisclosure, as the dome collector 2000. FIGS. 4A-4C are diagramsillustrating an example position of the dome collector 2000 within theBWR 100 according to at least some example embodiments. FIG. 5 is adiagram illustrating an example operation of the dome collector 2000.

Referring to FIGS. 3A-3C, the dome collector 2000 may include a lowersection 2010 and an upper section 2020. Further, the dome collector 2000may include an inner channel 2030 and an outer channel 2040. The outerchannel 2040 may also be referred to, herein, as exterior channel 2040.

A shape of the inner channel 2030 may be defined by inner side wall2035. A shape of the outer channel 2040 may be defined by the inner sidewall 2035 and outer side wall 2045. As is illustrated in FIGS. 3A-3C,surfaces of inner and outer side walls 2035 and 2045 within the lowersection 2010 are substantially straight or flat, and may taper towardsthe upper section 2020. As is illustrated in FIGS. 3A-3C, surfaces ofthe inner and outer side walls 2035 and 2045 within the upper section2020 may be curvilinear such that a cross-sectional shape of the uppersection 2020 is that of, for example, a closed circular or annular archor partial dome. For example at least a portion of the outer side wall2045 within the upper section 2020 of the dome collector may have asemi-torus shape. Further, at least a portion of the inner side wall2035 within the upper section 2020 of the dome collector may have asemi-torus shape. According to at least some example embodiments, theupper section 2020 is defined as the portion of the dome collector 2000above an intersection 2047 between the curvilinear and straight portionsof the outer side wall 2045, and the lower section 2010 is defined asthe portion of the dome collector 2000 below an intersection 2047between the curvilinear and straight portions of the outer side wall2045.

The upper section 2020 may include inlets 2050 that form paths from theinner channel 2030 to the exterior channel 2040, for example, throughthe inner side wall 2035. Further, the upper section 2020 may includeoutlets 2060 that form paths from the exterior channel 2040 out of thedome collector 2000, for example, through the outer side wall 2045.

As is illustrated in FIG. 4A, the dome collector 2000 may be positionedabove or, alternatively, directly above the separators 1000. FIG. 4Billustrates the dome collector 2000 and peripheral steam separators 1002from the same perspective described above with respect to FIG. 2 . As isillustrated in FIG. 4B, the upper section 2020 of the dome collector2000 may have a semi-torus shape, and the dome collector 2000 may bepositioned above or, alternatively, directly above the separators 1000such that the semi-torus shape of the upper section 2020 of the domecollector 2000 is vertically aligned with the peripheral steamseparators 1002 such that the inner channel 2030 is configured toreceive a gas-liquid two-phase FS (e.g., wet steam 600) from theperipheral steam separators 1002. For example, in the example shown inFIGS. 4A and 4B, the dome collector 2000 is positioned above thering-shaped (i.e., annular) arrangement of peripheral steam separators1002 such that points A and B of the dome collector 2000 are directlyabove points A′ and B′ of the ring-shaped arrangement of peripheralsteam separators 1002, respectively. As is shown in FIG. 4C, accordingto at least some example embodiments, the dome collector 2000, includingthe lower section 2010 and upper section 2020, may be defined by a2-dimensional shape 2002. According to at least some exampleembodiments, a shape of the dome collector 2000 may be defined byrotating the 2-dimensional shape 2002 about an axis 2004 in a circularpath having a radius 2006. The radius 2006 illustrated in FIG. 4C isprovided for the purpose of facilitating an explanation of an example ofthe dome collector 2000. A length of the radius 2006 is not limited tothe length illustrated in FIG. 4C. According to at least some exampleembodiments, a length of radius 2006 is set according to the preferencesof an operator of the BWR 100 and/or a designer of the dome collector2000.

Referring to FIG. 5 , FIG. 5 illustrates a portion of a first peripheralsteam separator 1002A as an example of the peripheral steam separators1002. FIG. 5 also illustrates a radial cross section of the domecollector 2000.

As is illustrated in FIG. 5 , the discharge section of the firstperipheral steam separator 1002A may be vertically aligned with thearch-shaped upper section 2020 of the dome collector 2000 such that wetsteam 600 that exits an upper end of the first peripheral steamseparator 1002A enters the inner channel 2030 of the dome collector2000. As is illustrated in FIG. 5 , the wet steam 600 passes from theinner channel 2030 to the arch-shaped portion of the exterior channel2040 within the upper section 2020 via inlets 2050. The first peripheralsteam separator 1002A illustrated in FIG. 5 extends in a direction thatis parallel to the axis 2004 of the dome collector 2000 illustrated inFIG. 4C, and perpendicular to the radius 2006 of the dome collector 2000illustrated in FIG. 4C. According to at least some example embodiments,some or all of the peripheral steam separators 1002 illustrated in FIG.5 extend in a direction that is parallel to the axis 2004 of the domecollector 2000 illustrated in FIG. 4C, and perpendicular to the radius2006 of the dome collector 2000 illustrated in FIG. 4C.

As is illustrated in FIG. 5 , once the wet steam 600 passes from theinner channel 2030 to the arch-shaped portion of the exterior channel2040 within the upper section 2020, separated water 700 may be removedfrom the wet steam 600. For example, due to the density differencebetween the liquid (i.e., water) and gas (i.e., steam) portions of thewet steam 600, the curvilinear shape of the exterior channel 2040 withinthe upper section 2020 may cause the water 700 to separate from the wetsteam 600, for example, when the wet steam impacts the curvilinearportion of the outer side wall 2045. As is illustrated in FIG. 5 , thewater 700 may flow out of the dome collector 2000 via the portions ofthe exterior channel 2040 within the lower section 2010. The wet steam600 from which the water 700 is separated becomes moisture-reduced steam800. The moisture-reduced steam 800 exits the dome collector 2000 viathe outlets 2060.

As is noted above, the wet steam 600 may be a gas-liquid two-phase FS inwhich the gas of the gas-liquid two-phase FS may be steam, and theliquid of the gas-liquid two-phase FS may be water. According to atleast some example embodiments, the moisture-reduced steam 800 is theportion of the wet steam 600 that remains after some or all moisture(i.e., water) has been removed from the wet steam 600. For example, themoisture-reduced steam 800 may be a gas-liquid two-phase FS thatincludes less entrained water than the wet steam 600. As anotherexample, the moisture-reduced steam 800 may be a gas-liquid two-phase FSthat includes significantly less entrained water than the wet steam 600(e.g., a reduction of 50% or more). For example, the moisture-reducedsteam 800 may be steam that includes about 10% moisture.

The BWR 100 may process the moisture-reduced steam 800 exhausted fromthe dome collector 2000 in the same manner explained above with respectto the steam that exits steam separators 1000 in the discussion of FIG.1 . For example, the moisture-reduced steam 800 is supplied to the steamdryer system 500 which may remove additional moisture from themoisture-reduced steam 800. For example, the steam dryer system 500 mayreceive moisture reduced steam 800 including about 10% moisture andremove much of the residual moisture such that the moisture reducedsteam 800 exiting the steam dryer system 500 may include, for example,0.1% or less moisture. The moisture-reduced steam 800 from whichmoisture is further removed by the steam dryer system 500 is exhaustedfrom the steam outlet nozzle 15 and drives the turbine 2, therebycausing electrical power to be generated by the generator joined to theturbine 2.

Further, the BWR 100 may process the water 700 separated by the domecollector 2000 in the same manner explained above with respect to thewater separated by steam separators 1000 in the discussion of FIG. 1 .For example, in the example shown in FIGS. 3A-5 , the water 700separated by the dome collector 2000 is mixed with the cooling watersupplied from the feed water inlet nozzle 17, descends the annular space9, and is introduced to the core 7 via the lower plenum 10.

Though, for the purpose of simplicity, only a single peripheral steamseparator 1002A is illustrated in FIG. 5 , all peripheral steamseparators 1002 may interact with, and/or be positioned with respect to,corresponding portions of the dome collector 2000 in the same mannerdiscussed below with respect to the first peripheral steam separator1002A. According to at least some example embodiments, a portion of thedome collector 2000 that corresponds to a particular steam separator isthe portion of the dome collector 2000 that is located in the vicinityof the particular steam separator, including, for example, the portionof the dome collector 2000 that is located directly above an upperopening of the particular steam separator.

FIGS. 3A-5 are explained above with respect to an example in which thedome collector 2000 is positioned directly above peripheral steamseparators 1002 among the steam separators 1000. However, according toat least some example embodiments, the dome collector 2000 may not bepositioned directly above the peripheral steam separators 1002, and maybe positioned directly above interior steam separators. As used herein,the term “interior steam separator” refers to a steam separator, fromamong the steam separators 1000, that is not one of the peripheral steamseparators 1002. Further, according to at least some example embodimentsthe dome collector 2000 may be positioned directly above both one ormore interior steam separators and one or more of the peripheral steamseparators 1002. Further, according to at least some example embodimentsthe dome collector 2000 may be positioned directly above one or more ofthe peripheral steam separators 1002 and none of the interior steamseparators. According to at least some example embodiments, any steamseparator, from among the steam separators 1000, may interact withcorresponding portions of the dome collector 2000 in the same mannerdiscussed below with respect to the first peripheral steam separator1002A.

Accordingly, the dome collector 2000 may reduce moisture carry-over,thereby preventing and/or reducing the exposure of components of the BWR100 (e.g., a main steam line and/or a turbine 2) to prolonged highradioactivity levels during operation of the BWR 100. Further, it may bedesirable to use the dome collector 2000 within a BWR that is performinguprated power generation. For example, in a BWR configured to performuprated power generation, a flow of coolant (e.g., light water)throughout the BWR may be increased, and thus, the moisture content ofwet steam produced by peripheral steam separators of the BWR may beincreased. The dome collector 2000 can remove water from the wet steamso as to reduce and/or prevent exposure of components of the BWR, whichis configured to perform uprated power generation, to prolonged highradioactivity levels caused, for example, by the radioactivity carriedby entrained water droplets.

According to at least some example embodiments, the material of any orall of the components of the dome collector 2000 may be stainless steel.For example, according to at least some example embodiments, the innerside wall 2035 and outer side wall 2045 (e.g., including inlets 2050and/or and outlets 2060) may be composed of stainless steel. Accordingto at least some example embodiments, the stainless steel of which thedome collector 2000 and/or components of the dome collector 2000 arecomposed may be type 304 stainless steel. Further, according to at leastsome example embodiments, any of inner walls of dome collector 2000(e.g., inner surfaces of the inner channel 2030, outer channel 2040,inlets 2050 and/or and outlets 2060), may be coated with an anti-foulingagent in order to minimize or reduce losses due to surface friction. Theanti-fouling agent may be TiO₂, which is described in U.S. PatentPublication No. 2010/0055308, the contents of which are incorporatedherein by reference.

Another example of an additional separation stage, an elbow extensionadditional separation stage, will now be discussed below with referenceto FIGS. 6A-7 .

Elbow Extension Additional Separation Stage

FIGS. 6A-6E illustrate various views of portions of an elbow extensionadditional separation stage 3000 according to at least some exampleembodiments. FIG. 7 is a diagram illustrating an example position of theelbow extension additional separation stage 3000 within the BWR 100according to at least some example embodiments. The elbow extensionadditional separation stage 3000 may also be referred to, in the presentdisclosure, as the elbow extension 3000. As will be discussed in greaterdetail below, according to at least some example embodiments, one ormore elbow extensions having the structure of the elbow extension 3000may be provided in addition to the separators 1000 to reduce the amountof water that is passed, within the gas-liquid two-phase FS, to at leastsome components of the BWR 100 (e.g., the dryer system 500, main steamline, and/or turbine 2).

FIG. 6A is a longitudinal cross section of the elbow extension 3000.FIG. 6B is a perspective view of the elbow extension 3000. FIGS. 6C and6D are views from above and below the elbow extension 3000,respectively. FIG. 6E is a view from in front of an exit portion of theelbow extension 3000. As is illustrated in FIGS. 6A, 6B and 7 , theelbow extension 3000 may be an extension of a steam separator from amongthe steam separators 1000. For example, the elbow extension 3000 may bea barrel that extends from a barrel of a steam separator from among thesteam separators 1000. According to at least some example embodiments,the elbow extension 3000 may be an extension of one of the peripheralsteam separators 1002. In the example shown in FIGS. 6A, 6B and 7 , theelbow extension 3000 is attached to a second peripheral steam separator1002B from among the peripheral steam separators 1002. According to atleast some example embodiments, the elbow extension 3000 may be attachedto an upper portion of the second peripheral steam separator 1002B(i.e., a portion of the second peripheral steam separator 1002B closestto the dryer system 500 in the example illustrated in FIG. 7 ).According to at least some example embodiments, the elbow extension 3000and second peripheral steam separator 1002B form a steam separationsystem.

According to at least some example embodiments, the elbow extension 3000is a barrel that includes a linear section 3010, a curved section 3020,an extension channel 3030, extraction holes 3040, and an exit portion3050.

As is illustrated in FIGS. 6A-6C and 7 , the linear section 3010 of theelbow extension 3000 may extend from the second peripheral steamseparator 1002B in a direction parallel, or substantially parallel, tothe direction in which the second peripheral steam separator 1002Bextends towards the elbow extension. Further, the curved section 3020 ofthe elbow extension 3000 may extend from the linear section 3010 and mayinclude a curve or bend having an angle of curvature θC. According to atleast some example embodiments, the angle of curvature θC refers to anangular difference between (i) a direction in which the elbow extension3000 extends before the curvature in the curved section 3020, and (ii) adirection in which the elbow extension 3000 extends after the curvaturein the curved section 3020 (e.g., at the exit portion 3050). Forexample, the view direction of FIG. 6E is parallel to the direction inwhich the elbow extension 3000 extends after the curvature in the curvedsection 3020. In the examples illustrated in FIGS. 6A-7 , the angle ofcurvature θC is 90°. However, according to at least some exampleembodiments, the angle of curvature θC may be less than or more than90°. For example, the angle of curvature may be 45° or 135°, or an anglein between 45° and 135°. According to at least some example embodiments,the angle of curvature θC may be chosen in accordance with thepreferences of an operator of the BWR 100 and/or a designer of the elbowextension 3000, for example, based on empirical information.

The extension channel 3030 is the interior region of the elbow extension3000. For example, the elbow extension 3000 may be a barrel, as is notedabove, and the extension channel 3030 may be the interior region of thebarrel. According to at least some example embodiments, a shape of theelbow extension 3000 at an interface region 3005 where the elbowextension 3000 interfaces with the peripheral steam separator 1002B maybe configured to interface with the shape of the second peripheral steamseparator 1002B. In the example shown in FIGS. 6A-6C and 7 , the elbowextension 3000 and the second peripheral steam separator 1002B are bothcylindrical (i.e., tubular) in shape at the interface region 3005.According to at least some example embodiments, the exit portion 3050 isthe end of the elbow extension 3000 opposite the interface region 3005.

As is illustrated in FIG. 6B wet steam 600 that exits the secondperipheral separator 1002B during operation of the BWR 100 may flow intothe channel 3030. Due to, for example, centripetal force exerted on thewet steam 600, water 700 is separated from the wet steam 600. Forexample, the above-referenced centripetal force may result from the wetsteam 600 flowing from the second peripheral separator 1002B throughextension channel 3030 and interacting with the concave portion 3032 ofthe extension channel 3030 within the curved section 3020 of the elbowextension 3000. The water 700 may flow out of the exit portion 3050.

According to at least some example embodiments, the elbow extension isarranged such that the exit portion 3050 points outward towards (e.g.,faces), for example, a portion of an interior surface of the cylindricaldryer skirt 350 nearest to the elbow extension 3000, or a portion of aninterior surface of the side wall of the pressure vessel 6 nearest tothe elbow extension 3000. Consequently, the water 700 flowing out theexit portion 3050 may be directed towards the dryer skirt 350 and/orside wall of the pressure vessel 6, and not towards the dryer system500. According to at least some example embodiments, the BWR 100 mayprocess the water 700 flowing out of the extension channel 3030 in thesame manner explained above with respect to the water separated by steamseparators 1000 in the discussion of FIG. 1 . In the example illustratedin FIGS. 6A-7 , the water 700 separated by the elbow extension 3000 ismixed with the cooling water supplied from the feed water inlet nozzle17, descends the annular space 9, and is introduced to the core 7 viathe lower plenum 10.

Further, the moisture-reduced steam 800 remaining after the separationof the water 700 from the wet steam 600 may exit the channel 3030 viathe extraction holes 3040 located in the convex portion (e.g., convexsurface) 3034 of the extension channel 3030 within the curved section3020 of the elbow extension 3000. Alternatively, the extraction holes3040 may be omitted from the elbow extension 3000, in which case themoisture-reduced steam 800 may exit the extension channel 3030 via theexit portion 3050.

According to at least some example embodiments, the BWR 100 may processthe moisture-reduced steam 800 that exits the elbow extension 3000 inthe same manner explained above with respect to the steam that exitssteam separators 1000 in the discussion of FIG. 1 . In the exampleillustrated in FIGS. 6A-7 , the moisture-reduced steam 800 that exitsthe elbow extension 3000 is supplied to the steam dryer system 500 whichmay remove additional moisture from the moisture-reduced steam 800, forexample, in a case where moisture-reduced steam 800 produced by theelbow extension 3000 still includes moisture. The moisture-reduced steam800 from which moisture is further removed by the steam dryer system 500is exhausted from the steam outlet nozzle 15 and drives the turbine 2,thereby causing power to be generated by the generator joined to theturbine 2.

Though, for the purpose of simplicity, only a single elbow extension3000 and a single peripheral steam separator 1002B are illustrated inFIGS. 6A, 6B and 7 , elbow extensions having the same structure andoperation described above with respect to the elbow extension 3000 maybe attached to any or all of the peripheral steam separators 1002 (or,any or all of the steam separators 1000), respectively. For example,according to at least some example embodiments, elbow extensionsaccording to example embodiments may not be attached to the peripheralsteam separators 1002, and may be attached only to the interior steamseparators, respectively. Further, elbow extensions according to exampleembodiments may be attached to one or more interior steam separators andone or more of the peripheral steam separators 1002, respectively.Further, according to at least some example embodiments the elbowextensions according to example embodiments may be attached to one ormore of the peripheral steam separators 1002, respectively, and attachedto none of the interior steam separators. Further, the elbow extensionsaccording to example embodiments may interact with (and be oriented withrespect to) the steam separators to which the elbow extensions areattached in the same manner discussed above with respect to the elbowextension 3000 and the second peripheral steam separator 1002B.

Accordingly, the elbow extension 3000 may reduce moisture carry-over,thereby preventing and/or reducing the exposure of components of the BWR100 (e.g., a main steam line and/or a turbine 2) to prolonged highradioactivity levels during operation of the BWR 100. Further, it may bedesirable to use one or more elbow extensions 3000 within a BWR that isperforming uprated power generation. For example, in a BWR configured toperform uprated power generation, a flow of coolant (e.g., light water)throughout the BWR may be increased, and thus, the moisture content ofwet steam produced by peripheral steam separators of the BWR may beincreased. The one or more elbow extensions 3000 can remove water fromthe wet steam so as to reduce and/or prevent exposure of components ofthe BWR, which is configured to perform uprated power generation, toprolonged high radioactivity levels caused, for example, by theradioactivity carried by entrained water droplets.

According to at least some example embodiments, the material of any orall of the components of the elbow extension 3000 may be stainlesssteel. For example, according to at least some example embodiments, thebarrel of the elbow extension (e.g., including the linear section 3010,curved section 3020, extension channel 3030, and an exit portion 3050)may be composed of stainless steel. According to at least some exampleembodiments, the stainless steel of which the elbow extension 3000and/or components of the elbow extension 3000 are composed may be type304 stainless steel. Further, according to at least some exampleembodiments, inner walls of the barrel of the elbow extension 3000(e.g., the extension channel 3030) and/or the extraction holes 3040 maybe coated with an anti-fouling agent in order to minimize or reducelosses due to surface friction. The anti-fouling agent may be TiO₂,which is described in U.S. Patent Publication No. 2010/0055308.

Another example structure for removing water from wet steam, streamlinedseparator pick-off rings, according to at least some example embodimentswill be discussed below with reference to FIGS. 8-10 .

Streamlined Steam Separator Including Pick-Off rings

FIG. 8 illustrates a streamlined steam separator that includes pickoffrings. According to at least some example embodiments, any or all of thesteam separators 1000 may have the structure of the steam separator4000. The steam separator 4000 includes a plurality of separator stagesincluding a first separator stage 4010, a second separator stage 4020,and a third separator stage 4030. The steam separator 4000 includes astandpipe 4100 through which the steam separator 4000 receives wet steam600. The wet steam passes through turning vanes 4200 included in thefirst separator stage 4010. Further, each of the plurality of separatorstages included in the steam separator 4000 is structured to removemoisture from the wet steam 600. For the purpose of simplicity, FIGS.8-10 will be explained with reference first through third separatorstages 4010-4030. However, the steam separator 4000 is not limited tohaving three separator stages. For example, according to at least someexample embodiments, the plurality of separator stages included in thesteam separator 4000 may have two separator stages. Further, accordingto at least some example embodiments, the plurality of separator stagesincluded in the steam separator 4000 may have more than three separatorstages.

For example, the steam separator 4000 may include a skirt 4300 and aseparator barrel 4400 inside the skirt 4300. As is illustrated in FIG. 8, the skirt 4300 and separator barrel 4400 may each be tubular in shape.Further, each of the first through third separator stages 4010-4030includes a moisture pick-off ring 4500. Using the third separator stage4030 as an example, the moisture pick-off ring 4500 of the thirdseparator stage 4030 includes a lip that protrudes from the skirt 4300past the separator barrel 4400 towards a central axis of the steamseparator 4000 so as to separate water 700 from the wet steam 600 bycapturing the water 700 and directing the water 700 through a dischargepassage 4600 formed by the space between the skirt 4300 and separatorbarrel 4400, as is illustrated in FIG. 8 . As is also illustrated inFIG. 8 , a path of the discharge passage 4600 includes one or moreopenings in the skirt 4300 through which the water 700 captured by thepick-off ring 4500 of the third separator stage 4030 exits the separator4000. The moisture pick-off rings 4500 of the first and second separatorstages 4010 and 4020 may operate in the same manner discussed above withrespect to the moisture pick-off ring 4500 of the third separator stage4030. Moisture-reduced steam 800 exits the steam separator 4000 throughan opening at the top end of the steam separator 4000 (i.e., the end ofthe steam separator opposite to the end at which the standpipe 4100 islocated). The moisture-reduced steam 800 that exits the top of theseparator 4000 is the portion of the wet steam 600 remaining after thewater 700 is removed by each of the plurality of separator stagesincluded in the steam separator 4000.

According to at least some example embodiments of the inventiveconcepts, any or all of the plurality of separator stages included inthe steam separator 4000 (including, for example, first through thirdseparator stages 4010-4030) may include a controlled expansion region4700. For the purpose of simplicity, FIGS. 8 and 9 are explained withreference, primarily, to the controlled expansion region 4700 of thethird separator stage 4030. However, according to at least some exampleembodiments, the description of the controlled expansion region 4700 ofthe third separator stage 4030 may apply to a controlled expansionregion 4700 of any separator stage in the steam separator 4000 thatincludes a controlled expansion region 4700. Item 4030A in FIG. 8illustrates an axial view of the controlled expansion region 4700 of thethird separator stage 4030 from a position above the third separatorstage 4030 looking down towards the standpipe 4100. Item 4030B in FIG. 8illustrates a side elevation view of the controlled expansion region4700 of the third separator stage 4030. Item 4030C in FIG. 8 illustratesan axial view of the controlled expansion region 4700 of the thirdseparator stage 4030 from a position below the third separator stage4030 looking up in the same direction in which the moisture-reducedsteam 800 flows out of the steam separator 4000.

Within the controlled expansion region 4700 of the third separator stage4030, a diameter of the third separator stage 4030 gradually increasesfrom a first diameter d1 to a larger second diameter d2. The firstdiameter d1 is the diameter of the moisture pick-off ring 4500 of thesecond separator stage 4020 that protrudes towards the central axis ofthe steam separator 4000. As is illustrated in FIG. 8 , the secondseparator stage 4020 also includes a controlled expansion region 4700.Within the controlled expansion region 4700 of the second separatorstage, a diameter of the second separator stage 4020 gradually increasesfrom the first diameter d1 to the larger second diameter d2. Accordingto at least some example embodiments, any separator stage having anadjacent lower separator stage may include a controlled expansion region4700.

FIG. 9 is a diagram for explaining the controlled expansion regions 4700between adjacent separator stages of the steam separator 4000 in greaterdetail. FIG. 9 illustrates an upper line 4710 and a lower line 4720.Lines 4710 and 4720 represent the contours of adjacent separator stageswithin the steam separator 4000. For the purpose of simplicity, FIG. 9will be explained with respect to an example in which lines 4710 and4720 represent the contours of the second and third separator stages4020 and 4030. However, lines 4710 and 4720 may represent the contoursof any adjacent separator stages.

Referring to FIG. 9 , lines 4710 and 4720 transition from beingseparated by the diameter d1 on the left to being separated by thelarger diameter d2 on the right. As is illustrated in FIG. 9 , thetransition from the first diameter d1 to the larger diameter d2 takesplace within the controlled expansion region 4700. Further, in theexample illustrated in FIG. 9 , the controlled expansion region 4700includes three sections: a first curved section L1, and angled sectionLR, and a second curved section L2. Within the first curved section L1,lines 4710 and 4720 transition from being parallel lines having thefirst diameter d1 to being the substantially straight and angled linesof the angled section LR. Within the second curved section L2, lines4710 and 4720 transition from being the substantially straight andangled lines of the angled section LR to being parallel lines having thesecond diameter d2. In the example shown in FIG. 9 , the degree to whichthe angled lines in the angled section LR are angled relative to theportions of lines 4710 and 4720 in which lines 4710 and 4720 areparallel is expressed as half angle α/2. In the example shown in FIG. 9, the controlled expansion region 4700 has total length L. Consequently,the transition from the first diameter d1 to the second diameter d2takes place gradually over the length L.

FIG. 10 is a diagram for explaining adjacent separator stages that lacka controlled expansion region. FIG. 10 illustrates an upper line 4730and a lower line 4740. As is illustrated in FIG. 10 , lines 4730 and4740 are arranged in the same manner as lines 4710 and 4720 of FIG. 9 ,with the exception that lines 4730 and 4740 lack a controlled expansionregion 4700. Consequently, the change between the first and seconddiameters d1 and d2 in lines 4730 and 4740 is abrupt, and not gradual.Some conventional steam separators include adjacent separator stageshaving contours corresponding to the upper and lower lines 4730 and 4740of FIG. 10 . Further, the abrupt diameter change causes a substance(e.g., wet steam) that flows through a pair of adjacent separator stageshaving contours corresponding to the upper and lower lines 4730 and 4740of FIG. 10 to experience pressure loss.

In comparison, the steam separator 4000 of FIG. 8 is streamlined withrespect to a conventional steam separator that includes separator stageshaving the contours discussed above with respect to FIG. 10 . Forexample, a substance (e.g., wet steam) that flows through a pair ofadjacent separator stages having contours corresponding to the upper andlower lines 4710 and 4720 (e.g., the first and second separator stages4010 and 4020, or the second and third separator stages 4020 and 4030)may experience substantially reduced pressure loss due to the gradualdiameter change provided by the controlled expansion region 4700.According to at least some example embodiments, the reduction inpressure loss increases as the half angle α/2 becomes smaller.Additionally, with respect to wet steam, according to at least someexample embodiments, the controlled expansion region 4700 may reduce oreliminate flow separation and annular recirculation regions at pointswhere adjacent separator stages of the streamlined steam separator 4000interface with each other. Further, with respect to wet steam, accordingto at least some example embodiments, the controlled expansion region4700 may reduce or eliminate re-entrainment of separated liquid fromrolling waves at points where adjacent separator stages of thestreamlined steam separator 4000 interface. Further, according to atleast some example embodiments, the elimination of abrupt diametertransitions within the streamlined steam separator 4000 improves watersegregation. Further, the controlled expansion region 4700 may preventan increase to moisture carry-over that would be caused by moisturecondensation resulting from the large pressure drop which wouldotherwise occur in the vicinity of the pick-off rings of the separatorstages of the steam separator 4000.

According to at least some example embodiments, the material of any orall of the components of the streamlined steam separator 4000 may bestainless steel. For example, according to at least some exampleembodiments, the skirt 4300 and the barrel 4400 may be composed ofstainless steel. Further, according to at least some exampleembodiments, the moisture pick-off rings 4500 and the controlledexpansion region 4700 of each of the plurality of separator stages inthe steam separator 4000 may be composed of stainless steel. Accordingto at least some example embodiments, the stainless steel of which thestreamlined steam separator 4000 and/or components of the streamlinedsteam separator 4000 are composed may be type 304 stainless steel.Further, according to at least some example embodiments, inner walls ofthe barrel 4400, inner walls of the controlled expansion regions 4700,and/or inward-facing portions of the moisture pick-off rings 4500 may becoated with an anti-fouling agent in order to minimize or reduce lossesdue to surface friction. The anti-fouling agent may be TiO₂, which isdescribed in U.S. Patent Publication No. 2010/0055308.

Example embodiments thus being described, it will be appreciated by oneskilled in the art that example embodiments may be varied throughroutine experimentation and without further inventive activity.Variations are not to be regarded as a departure from the spirit andscope of the example embodiments, and all such modifications as would beobvious to one skilled in the art are intended to be included within thescope of the following claims.

We claim:
 1. A steam separator comprising: a skirt; a barrel inside theskirt; a first separator stage; and a second separator stage adjacent tothe first separator stage, the first separator stage including a firstpick-off ring that protrudes from the skirt past the barrel towards aninterior of the steam separator, the second separator stage including aninner surface which has a diameter that gradually increases from a firstdiameter value at a first portion of the second separator stage to asecond diameter value at a second portion of the second separator stage.2. The steam separator of claim 1 wherein, the first portion of thesecond separator stage is a portion of the second separator stageadjacent to the first pick-off ring of the first separator stage, andthe second portion of the second separator stage is a portion of thesecond separator located farther away from the first pick-off ring ofthe first separator stage than the first portion.
 3. The steam separatorof claim 2 wherein, the first diameter value is equal to a diametervalue of an inner surface of the first pick-off ring.
 4. The steamseparator of claim 1 further comprising: a standpipe connected to thefirst separator stage, wherein the first separator stage furtherincludes turning vanes, the standpipe being connected to an end of thefirst separator stage opposite an end of the first separator stage atwhich the first pick-off ring is located.
 5. A nuclear boiling waterreactor comprising: a reactor pressure vessel; a core in the reactorpressure vessel; and one or more steam separators according to claim 1located above the reactor core.